This invention relates to synchronizing apparatus for television apparatus and more particularly to television cameras and other apparatus such as video tape machines having a "gen-lock" reference input.
The "gen-lock" is a composite signal containing the horizontal phasing, vertical phasing, and color burst information. A typical television camera head contains circuitry for generating a composite video signal including the horizontal and vertical sync and the color burst signal. The "gen-lock" input terminal of the camera is used to cause the camera to be placed in time coincidence with this "gen-lock" reference signal. The camera may operate on its own reference signals when used, for example, for video tape recording or may be synchronized to a reference via its "gen-lock" input terminal. The camera head may be located at various locations which may be remote from a central or camera control unit location. Cable is usually coupled from this control location to the camera head. The local reference at the control location is coupled to the "gen-lock" input terminal of the camera head and the composite video from the camera head is coupled via a cable to the central control point which may be located at a video switcher. The camera cable length is changeable and this changeability of the cable length produces timing problems at the video switcher. Applicant herein provides a solution to this problem which is convenient and is readily adaptable for use with the existing "gen-lock" input terminal at the camera head.
It is known in the prior art to provide a synchronizing apparatus for compensating for horizontal sync changes for varying cable lengths. This is illustrated, for example, in U.S. Pat. No. 3,429,994 of D. A. Pay et al or No. 3,368,034 of R. A. Dischert et al. These systems do not correct for color phase. The camera head circuitry itself is specially modified for handling the sync signals.
Hathaway, U.S. Pat. No. 3,424,866 describes a synchronizing apparatus for compensating for sync using submultiple frequencies of the horizontal line repetition rate to permit the synchronizing signal to be transmitted over an audio circuit. Although, Brown, U.S. Pat. No. 3,493,680 describes color phase locking via an audio circuit, these signals are neither composite sync and burst signals nor composite sync and burst as normally associated with a "gen-lock" signal and therefore not adaptable for use at the "gen-lock" input of a typical camera head.